<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 200px;
      height: 200px;
      border: 10px solid red;
      border-radius:110px
    }
    #d2{

      width: 100px;
      height: 100px;
      border: 1px solid red;
      padding-left: 50px;
      padding-top: 50px;
      /*添加此样式后 给元素添加边框和内边距时不会影响元素的宽高*/
      box-sizing: border-box;
    }

  </style>

</head>
<body>
<div id="d2">内边距</div>
<div id="d1">边框测试</div>

</body>
</html>